Implementation of a CANopen Interface for the Control of an Elevator System

The paper describes the realisation of a CANopen based control system of an elevator operating in an automatic storage system of a factory. The elevator is actuated by two asynchronous motors which were originally handled by a motor drive system connected to a master device via a RS485 interface by means of a proprietary communication protocol. The realised CANopen based control system allows for the motors drive system to be interfaced to a CAN fieldbus, using the CANopen device profile for I/O modules, as a slave exchanging input/output signals with a master device. In practice, it has been implemented a protocol converter which makes accessible via CANopen all the variables normally exchanged by means of the proprietary protocol. The control system comprises a CANopen interface for the motor drive system based on two hardware components: a microprocessor and a CAN controller, which are products normally in commerce. The paper reports in detail the criteria used to select the most suitable CANopen device profile for the application and the components of the CANopen interface. Moreover, the paper analyses the firmware implementation paying particular attention to how commands, statuses and parameters specified by the proprietary protocol could be exchanged via CAN by means of the protocol converter. Finally, the paper describes an application for handling the elevator implemented as a software package for Personal Computer using a commercially available CANopen master board.